1. Field of the Invention
The present invention relates to a magnetic resonance diagnosing apparatus for obtaining morphologic data such as a slice image and function data such as spectroscopy of a patient (living body) by utilizing a magnetic resonance (MR) phenomenon.
2. Description of the Related Art
Diagnosis data obtained by a magnetic resonance diagnosing apparatus is morphologic data and function data. Morphologic data is a scano-image, a slice image, or a three-dimensional image of a desired portion of a patient. Function data is spectroscopy or a spectroscopic image The former reflects the density distribution, and the like, of a specific atomic nucleus, e.g., proton. The latter is analytic data of a plurality of chemical compounds including a specific atomic nucleus. In general, morphologic data is called magnetic resonance imaging (MRI), and function data is called magnetic resonance spectroscopy (MRS). Spectroscopic imaging is particularly called MRSI.
The data precision of MRI or MRS is determined depending on the characteristics of a static magnetic field as a basic magnetic field condition to cause an MR phenomenon, the characteristics of an RF pulse used to determine, e.g., the position where the MR phenomenon is to be caused, the characteristics of a gradient magnetic field which adds position data to an MR signal, and the like. Various techniques have been proposed to improve these characteristics. Some techniques have been realized and put into practice as they are incorporated in magnetic resonance diagnosing apparatuses. A typical technique of this type is the one for improving the uniformity of the static magnetic field. According to this technique, a shim coil is provided in addition to a static magnetic field coil (main coil). A correction current is supplied to the shim coil in order to correct the magnetic field generated by the main coil.
However, these techniques including the above-mentioned one for improving the uniformity of the static magnetic field are correction techniques by means of calculation. The data precision using these techniques is thus limited. In addition, it is impossible to perform correction that can cope with changes over time or individual patient's difference. Moreover, in the case of MRS that requires high uniformity in the static magnetic field, a sufficient effect cannot be obtained with these techniques.